1. Field of the Invention
The present invention pertains to a method and apparatus for supplying a manufacturing operation with materials in different forms through a single off-loading station.
2. Brief Description of the Prior Art
Large scale manufacturing operations frequently require the continuous supply of materials and fuel used in the manufacturing process, which materials must be delivered to the site of the manufacturing operation on a fairly continuous basis. A paper plant is typical of such operations, as wood fiber materials in large quantities are consumed daily in the paper manufacturing process. Daily consumption rates on the order of 5,000 tons of fiber materials are not uncommon for modern, large scale operations. The wood fiber material is usually received at the paper plant site in either chip form or in "roundwood", that is, logs. The roundwood is subsequently reduced to ship form and the chips are processed to form a fiber slurry which is fed to the paper making machine.
FIG. 1 is a schematic of a typical pulp paper plant layout. In FIG. 1, railroad track systems A and B with attendant off-loading facilities are used for supplying roundwood and a separate track system C for supplying fiber material in chip form. This conventional separation of receiving stations for chips and roundwood reflected the different process paths taken by the two wood fiber material forms and has necessitated the expenditure of substantial sums for duplicate railroad systems and material handling and conveying apparatus. Potential cost savings exist for a system and apparatus such as that described in the present invention which can accomplish the supply of different raw materials through a single off-loading station.
The present trend is to consolidate pulp paper plants such as shown in FIG. 1 with wood processing plant operations to make more effective use of the residual by-products from the wood processing plants. Wood processing plants typically produce finished wood items such as lumber, plywood, etc. with the wood residues going to produce chips and the bark going to provide fuel for the associated pulp paper plants. Hence, for such combined operations, the roundwood received at the off-loading stations would be in tree-length form as well as the 5 feet, 3 inch standardized pulp wood length. The method and apparatus described herein can advantageously and economically handle tree-length roundwood as well as pulp wood-length logs.
The usual manner of conveyance of the wood fiber raw materials to a pulp paper plant is by means of open-topped railroad cars, as can be appreciated from a review of FIG. 1. However, in certain situations it may be more economically advantageous to ship by highway truck-trailer, especially in view of the rigid rate structure under which present railroad shipments must conform. This economic advantage is pronounced for combined wood product and pulp paper plants since the rate for transporting roundwood by rail in tree-lengths is disproportionately greater than the cost for rail-transporting roundwood in pulp wood-lengths, reflecting the higher potential finished value of the products exiting the wood product plant. Hence, the method and apparatus disclosed herein for unloading wood fiber material delivered in both railroad cars and highway truck-trailers is particularly advantageous.
The unloading of the fiber matrial-laden, open-topped railroad cars in pulp paper plants can be accomplished by the use of a rotary railroad car dumper equipped with an elevated receiver box, such as shown in U.S. Pat. No. 3,993,203 to Bartley. Advantages of such rotary railroad car dumpers, having apparatus for inverting the entire railroad car and causing the contents to spill into the captive receiver box, include relatively short cycle times, maintenance of the orderly stacking of tree-length roundwood subsequent to the inversion of the railroad car, and reduction in the overall waste of fiber material that occurs each time the material is placed in unconfined storage, such as on the ground. The method and apparatus of the present invention enables the full benefits of such rotary dumpers to be realized.